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Refraction of waves
Intermediate
Waves change direction when speed changes.
n₁sinθ₁ = n₂sinθ₂When a wave enters a medium with a different speed, its direction bends and its wavelength changes while frequency stays the same. Snell: sinθ₁/sinθ₂ = v₁/v₂.
Water waves bending toward the shore as depth decreases.
Bends toward the normal in the slower medium.
In more detail
When a wave passes from one medium to another, its speed and wavelength change while its frequency stays the same. The change in direction is governed by Snell's law.
Real-world uses
- Lenses focus light by refraction, and sound horns refract waves.
- Seismic waves refract as they travel through layers of the Earth.
- Light bending as it enters water from air is refraction, and the same rule explains how a swimming pool looks shallower.
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Frequently asked questions
Does frequency change in refraction?
No. The frequency stays fixed, while speed and wavelength change.
Why does a wave bend?
Because one side of the wavefront enters the new medium first and changes speed earlier.
Why does a wave bend when it changes speed?
Its wavefronts change direction because one side of the wave enters the new medium first and slows down sooner.
Related topics in Waves & Sound
Speed of sound in gases · Reflection of waves · Phase change on reflection · Diffraction · Principle of superposition · Constructive and destructive interference